FAS activation induces dephosphorylation of SR proteins; dependence on the de novo generation of ceramide and activation of protein phosphatase 1
| Autor: | C E, Chalfant, B, Ogretmen, S, Galadari, B J, Kroesen, B J, Pettus, Y A, Hannun |
|---|---|
| Rok vydání: | 2001 |
| Předmět: |
Threonine
Diacylglycerol Kinase Sphingolipids Time Factors Blotting Western Carboxylic Acids Palmitic Acid Ceramides Fumonisins Phosphoric Monoester Hydrolases Cell Line Enzyme Activation Jurkat Cells Sarcoplasmic Reticulum Protein Phosphatase 1 Phosphoprotein Phosphatases Serine Humans Electrophoresis Polyacrylamide Gel Protein Phosphatase 2 fas Receptor Enzyme Inhibitors Phosphorylation |
| Zdroj: | The Journal of biological chemistry. 276(48) |
| ISSN: | 0021-9258 |
| Popis: | The search for potential targets for ceramide action led to the identification of ceramide-activated protein phosphatases (CAPP). To date, two serine/threonine protein phosphatases, protein phosphatase 2A (PP2A) and protein phosphatase 1 (PP1), have been demonstrated to function as ceramide-activated protein phosphatases. In this study, we show that treatment with either anti-FAS IgM (CH-11) (150 ng/ml) or exogenous d-(e)-C(6-)ceramide (20 microm) induces the dephosphorylation of the PP1 substrates, serine/arginine-rich (SR) proteins, in Jurkat acute leukemia T-cells. The serine/threonine protein phosphatase inhibitor, calyculin A, but not the PP2A-specific inhibitor, okadaic acid, inhibited both FAS- and ceramide-induced dephosphorylation of SR proteins. Anti-FAS IgM treatment of Jurkat cells led to a significant increase in levels of endogenous ceramide beginning at 2 h with a maximal increase of 10-fold after 7 h. A 2-h pretreatment of Jurkat cells with fumonisin B(1) (100 microm), a specific inhibitor of CoA-dependent ceramide synthase, blocked 80% of the ceramide generated and completely inhibited the dephosphorylation of SR proteins in response to anti-FAS IgM. Moreover, pretreatment of Jurkat cells with myriocin, a specific inhibitor of serine-palmitoyl transferase (the first step in de novo synthesis of ceramide), also blocked FAS-induced SR protein dephosphorylation, thus demonstrating a role for de novo ceramide. These results were further supported using A549 lung adenocarcinoma cells treated with d-(e)-C(6-)ceramide. Dephosphorylation of SR proteins was inhibited by fumonisin B(1) and by overexpression of glucosylceramide synthase; again implicating endogenous ceramide generated de novo in regulating the dephosphorylation of SR proteins in response to FAS activation. These results establish a specific intracellular pathway involving both de novo ceramide generation and activation of PP1 to mediate the effects of FAS activation on SR proteins. |
| Databáze: | OpenAIRE |
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